Estimation of endoplasmic reticulum aminopeptidase 1 level of expression in lesional and nonlesional skin of psoriatic patients and healthy controls

Abstract

Background Psoriasis is a chronic inflammatory autoimmune disease of the skin, in which an elevated expression of endoplasmic reticulum aminopeptidase 1 (ERAP1), an enzyme involved in the final processing of major histocompatibility complex-I ligands, was reported. No previous reports studied the level of ERAP1 in lesional and nonlesional skin of psoriatic patients. Objective To estimate the level of ERAP1 expression in lesional and nonlesional skin of psoriatic patients and the skin of healthy controls to define its role in the pathogenesis of psoriasis. Patients and methods In this case–control study, 25 psoriatic patients and 30 healthy, age-matched and sex-matched controls were enrolled. All patients were subjected to detailed history and clinical examination, including Psoriasis Area and Severity Index (PASI) score to determine severity of psoriasis. Skin biopsies were obtained from all participants: two from psoriatic patients (lesional and nonlesional) and one from healthy controls. ERAP1 level was measured using PCR technique. Results There was a highly significant level of expression of ERAP1 in psoriatic lesions when compared with control skin (P<0.001). Moreover, ERAP1 in nonlesional tissue in psoriatic patients was significantly higher than in controls (P<0.001). ERAP1 expression in lesional tissue was higher than that in nonlesional tissue, but without a significant difference. Moreover, a positive correlation was detected between lesional tissue ERAP1 level and PASI score. Nonlesional tissue ERAP1 also correlated positively with the PASI score. Conclusion This study, which is the first to measure tissue ERAP1 expression, demonstrated an increased expression in psoriatic skin, in addition to its positive correlation with disease severity. This implied the role of ERAP1 in the pathogenesis of psoriasis, thus encouraging the study of future treatment modalities targeting ERAP1 pathway that could revolutionize treatment for psoriasis.